The present invention relates to the isolation and/or identification of stem cells having adipocytic, chondrocytic and pancreatic differentiation potential, and the use of these stem cells.
Mesenchymal stem cells (MSC), also known as mesenchymal stromal cells, are multipotent cells which have the ability under suitable in vitro and in vivo conditions to differentiate into various mesenchymal tissues. Thus for example they can differentiate into osteocytes, chondrocytes, adipocytes and myocytes and form bone, cartilage, fat and muscle tissue. In addition however, they can also differentiate into astrocytes, neurones, endothelial cells, hepatocytes, pancreas-like cells and pulmonary epithelial cells. Morphologically, they can be identified by their fibroblastoid phenotype and can be found in various adult and embryonic tissues in man, inter alia in the brain, bone marrow, umbilical cord blood, blood vessels, skeletal muscle, the skin, liver, gums and placenta.
MSC express a range of surface markers such as for example CD105 (endoglin, SH2), CD73 (ecto-5′-nucleotidase, SH3, SH4), CD166 (ALCAM), CD29 (β1 integrin), CD44 (H-CAM) and CD90 (Thy-1), some of which can also be found on endothelial and epithelial cells and on muscle cells. However, MSC can be distinguished from hematopoietic stem cells since MSC do not express the markers CD45, CD34 and CD133 specific for hematopoietic stem cells.
Mesenchymal stem cells have the property of rapidly and stably adhering to plastic or glass surfaces and forming colony-forming fibroblasts (“colony-forming units” (CFU-F)). However, the latter are heterogeneous in terms of their proliferation and differentiation capabilities.
Mesenchymal stem cells with a specific differentiation potential are of great interest in medicine and research: they can in particular be obtained from bone marrow, even from the elderly, have a high division rate and as aforesaid can differentiate into tissue cells of mesenchymal origin. Therefore for example in the context of stem cell therapies they could be used directly in the treatment of degenerative diseases of organs such as bone, cartilage, tendons, muscle, connective tissue, blood cells etc.
For the obtention or isolation of mesenchymal stem cells, unfractionated bone marrow cells which are cultured on plastic dishes are currently used as the starting material, the MSC are identified by their adhesion to the plastic surface, and the non-adhering hematopoietic cells are discarded from the sample. The cells obtained in this way are however less defined and differentiate not only into heterogeneous MSC populations, but also into osteoblasts, and/or osteoblast precursor cells, fat cells, reticular cells, macrophages and endothelial cells. Specific treatment of degenerative diseases of an organ with MSC without specific differentiation potential is thus difficult or impossible because of possible side-effects.
The isolation of mesenchymal stem cells with completely specific differentiation potential was not previously known or possible in the state of the art. However, as aforesaid, such isolation would have the great advantage that stem cells thus identified could be selectively used for the therapy/treatment of diseased, degenerated or damaged tissues into which the stem cells thus specifically isolated differentiate.
Thus for example cartilage damage could be treated by introducing specifically isolated mesenchymal stem cells with chondrogenic differentiation potential either directly in situ into the affected tissue, where they differentiate into chondrocytes and thus replace the damaged tissue (stem cell therapy). On the other hand, however, differentiation into chondrocytes in vitro can also be of interest if the aim is to obtain differentiated chondrocytes, for example for research/diagnosis/medicine.
Against this background there is great interest in mesenchymal stem cells with specific differentiation potential, in particular in order to use them in appropriate applications.
An object of the present invention is therefore to provide new ways whereby mesenchymal stem cells with a specific differentiation potential can be isolated.